Battery separator, method of manufacturing a battery separator, battery, battery pack, and electronic apparatus

ABSTRACT

A battery separator includes a porous base material and a heat-resistant layer. The porous base material includes a first surface, a second surface opposed to the first surface, and a hole. The hole is formed in the porous base material and causes the first surface and the second surface to communicate with each other. The heat-resistant layer is configured to cover at least the first surface and a surface of the hole. The heat-resistant layer is formed of an inorganic material and deposited by an atomic layer deposition method.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 13/364,097, which was filed on Feb. 1, 2012, and which claimspriority to Japanese Priority Patent Application JP 2011-023686 filed inthe Japan Patent Office on Feb. 7, 2011, and Japanese Priority PatentApplication JP 2011-039711 filed in the Japan Patent Office on Feb. 25,2011, the entire contents of which are hereby incorporated by reference.

BACKGROUND

The present disclosure relates to a battery separator interposed betweena positive electrode and a negative electrode, a method of manufacturinga battery separator, a battery including the battery separator, abattery pack, and an electronic apparatus.

For example, a generally-used lithium-ion secondary battery includes apositive electrode containing a lithium composite oxide, a negativeelectrode containing a material capable of absorbing and releasinglithium ions, a separator interposed between the positive electrode andthe negative electrode, and a non-aqueous electrolyte solution. Thepositive electrode and the negative electrode are laminated on eachother via the separator or wound after the lamination, to thereby form acolumnar wound electrode. The separator plays a role in electricallyisolating the positive electrode and the negative electrode from eachother and a role in holding the non-aqueous electrolyte solution. As theseparator of such a lithium-ion secondary battery, a microporouspolyolefin membrane is generally used.

The microporous polyolefin membrane exhibits excellent electricalinsulation property and ion permeability and therefore it has beenwidely used as a separator of the lithium-ion secondary batterydescribed above, a capacitor, and the like. The lithium-ion secondarybattery has high power density and high capacitance density. However,since the lithium-ion secondary battery uses an organic solvent for anon-aqueous electrolyte solution, the non-aqueous electrolyte solutionmay be decomposed due to heat generated under abnormal conditions suchas short circuit and overcharge, which may lead to ignition in the worstcase. To prevent such a situation, some safety functions areincorporated into the lithium-ion secondary battery, one of which is ashutdown function of a separator.

The shutdown function of a separator is a function of, when a batterygenerates abnormal heat, clogging minute pores of the separator bythermal fusion or the like of a resin material and suppressing ionconduction in the non-aqueous electrolyte solution, to thereby stop theprogress of an electrochemical reaction. Generally, a lower shutdowntemperature provides higher safety, and one of reasons why polyethyleneis used as a component of a separator is that polyethylene has anappropriate shutdown temperature. In such a separator, for example, aresin film uniaxially or biaxially stretched is used so as to obtainporous property and improve strength.

In the case of shutdown, however, the separator is shrunk, and thereforethe positive electrode and the negative electrode come into contact witheach other, which may cause a secondary failure such as internal shortcircuit. Therefore, it has been demanded to reduce thermal contractionby improving heat resistance of the separator, and thus to improvesafety.

For example, Japanese Patent Application Laid-open No. 2009-16279discloses a separator including a covering layer in which a fineskeleton of a polyolefin resin is covered with a glass layer. Further,Japanese Patent No. 3797729 discloses a battery separator in which aninorganic thin film is formed by a sol-gel method on the surface of apolyolefin porous film without clogging a hole.

SUMMARY

In view of the circumstances as described above, it is desirable toprovide a battery separator excellent in heat resistance, a method ofmanufacturing a battery separator, a battery including the batteryseparator, a battery pack, and an electronic apparatus.

According to an embodiment of the present disclosure, there is provideda battery separator including a porous base material and aheat-resistant layer.

The porous base material includes a first surface, a second surfaceopposed to the first surface, and a hole that is formed in the porousbase material and causes the first surface and the second surface tocommunicate with each other.

The heat-resistant layer is configured to cover at least the firstsurface and a surface of the hole. The heat-resistant layer is formed ofan inorganic material and deposited by an atomic layer depositionmethod.

In the battery separator, since the heat-resistant layer is formed bythe atomic layer deposition method, the heat-resistant layer can beformed not only on the surface of the base material but also on thesurface of the hole within the base material. Accordingly, as comparedto the case where the heat-resistant layer is formed only on the surfaceof the base material, heat resistance of the separator can be improved.

It should be noted that “to cover a surface” means that, without beinglimited to the case of covering the entire surface, a part of thesurface only needs to be covered as long as desired heat resistance isobtained.

The heat-resistant layer may cover the first surface, the secondsurface, and the surface of the hole.

Accordingly, the heat resistance of the separator can be additionallyimproved.

It should be noted that the separator may include a hole that isprovided to at least one of the first surface and the second surface anddoes not cause the first surface and the second surface to communicatewith each other, in addition to the hole that causes the first surfaceand the second surface to communicate with each other. Further, the holethat does not cause the first and second surfaces to communicate witheach other may also be provided with the heat-resistant layer.

The thickness of the heat-resistant layer is not particularly limitedand is 2 nm or more and 10 nm or less, for example. In the case wherethe thickness of the heat-resistant layer is less than 2 nm, there maybe a case where the heat resistance is not improved depending on a basematerial. Further, a contact angle becomes large, and thus anelectrolyte is difficult to penetrate into the hole of the separator. Onthe other hand, in the case where the thickness of the heat-resistantlayer exceeds 10 nm, it is difficult to stably obtain a primary shutdownfunction of the separator depending on a base material. However, in thecase where an inner diameter of the hole is large, e.g., 100 nm or more,the thickness of the heat-resistant layer may exceed 10 nm (for example,20 nm). As long as the shutdown function of the separator can beensured, the thickness of the heat-resistant layer can be set asappropriate in accordance with the inner diameter of the hole.

The thickness of the first surface, that of the second surface, and thatof the heat-resistant layer covering the surface of the hole may bealmost uniform or different from one another. In the case where thefirst surface, the second surface, and the heat-resistant layer aredifferent in thickness from one another, for example, the thickness ofthe heat-resistant layer that covers the first surface (or secondsurface) may be larger than that of the heat-resistant layer that coversthe surface of the hole.

Further, the heat-resistant layer that covers the surface of the holemay be formed in an almost uniform thickness or may have a distributionof thickness. For example, as a distance from the first surface and thesecond surface is increased in the hole, the thickness of theheat-resistant layer may be gradually reduced. Alternatively, in theheat-resistant layer that covers the surface of the hole, the thicknessof the heat-resistant layer formed at the center in the thicknessdirection of the separator may be smaller than that of other portions.With this structure, a space is generated in the hole of the separator,with the result that air resistance can be reduced (a degree ofpenetration of the electrolyte solution is increased) while heatresistance is ensured.

Examples of the inorganic material that forms the heat-resistant layerinclude an aluminum oxide, a silicon oxide, and a titanium oxide. Thosematerials enhance the heat resistance of the base material and allow afilm to be formed by the atomic layer deposition method.

According to an embodiment of the present disclosure, there is provideda method of manufacturing a battery separator, including preparing aporous base material including a first surface, a second surface opposedto the first surface, and a hole that is formed in the porous basematerial and causes the first surface and the second surface tocommunicate with each other.

A heat-resistant layer is formed by an atomic layer deposition method,the heat-resistant layer being configured to cover at least the firstsurface and a surface of the hole and being formed of an inorganicmaterial.

In the method of manufacturing a battery separator, since theheat-resistant layer is formed by the atomic layer deposition method,the heat-resistant layer can be formed not only on the surface of thebase material but also the surface of the hole within the base material.Accordingly, as compared to the case where the heat-resistant layer isformed only on the surface of the base material, heat resistance of theseparator can be improved.

According to an embodiment of the present disclosure, there is provideda battery including a positive electrode, a negative electrode, anelectrolyte layer, and a separator.

The electrolyte layer is arranged between the positive electrode and thenegative electrode.

The separator includes a porous base material and a heat-resistantlayer.

The porous base material includes a first surface opposed to thepositive electrode, a second surface opposed to the negative electrode,and a hole that is formed in the porous base material and causes thefirst surface and the second surface to communicate with each other. Theheat-resistant layer covers at least the first surface and a surface ofthe hole. The heat-resistant layer is formed of an inorganic materialand deposited by an atomic layer deposition method.

According to an embodiment of the present disclosure, there is provideda battery pack including a battery, a control unit, and a package body.

The battery includes a positive electrode, a negative electrode, anelectrolyte layer, and a separator. The electrolyte layer is arrangedbetween the positive electrode and the negative electrode. The separatorincludes a porous base material and a heat-resistant layer. The porousbase material includes a first surface opposed to the positiveelectrode, a second surface opposed to the negative electrode, and ahole that is formed in the porous base material and causes the firstsurface and the second surface to communicate with each other. Theheat-resistant layer covers at least the first surface and a surface ofthe hole. The heat-resistant layer is formed of an inorganic materialand deposited by an atomic layer deposition method.

The control unit is configured to control charge and discharge of thebattery.

The package body is configured to support the battery and the controlunit.

According to an embodiment of the present disclosure, there is providedan electronic apparatus including a battery and a power receivingcircuit.

The battery includes a positive electrode, a negative electrode, anelectrolyte layer, and a separator. The electrolyte layer is arrangedbetween the positive electrode and the negative electrode. The separatorincludes a porous base material and a heat-resistant layer. The porousbase material includes a first surface opposed to the positiveelectrode, a second surface opposed to the negative electrode, and ahole that is formed in the porous base material and causes the firstsurface and the second surface to communicate with each other. Theheat-resistant layer covers at least the first surface and a surface ofthe hole. The heat-resistant layer is formed of an inorganic materialand deposited by an atomic layer deposition method.

The power receiving circuit is configured to receive power supply fromthe battery.

According to the present disclosure, heat resistance of a separator canbe improved.

Additional features and advantages are described herein, and will beapparent from the following Detailed Description and the figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a perspective view, partially broken away, showing an internalstructure of a battery including a battery separator according to anembodiment of the present disclosure;

FIG. 2 is a schematic cross-sectional view taken along the line I-I ofFIG. 1;

FIG. 3 is a schematic cross-sectional view showing an example of thestructure of the battery separator;

FIG. 4 is a schematic cross-sectional view showing another example ofthe structure of the battery separator;

FIG. 5 is a schematic cross-sectional view for describing an internalstructure of the battery separator shown in FIG. 4;

FIG. 6 is a table of experiment results showing a relationship among athickness of a heat-resistant layer, air resistance, and a contact anglewith respect to dimethyl carbonate (DMC);

FIG. 7 is a diagram for describing the contact angle;

FIG. 8 is a graph showing experiment results obtained by evaluatingheat-resistance characteristics of samples shown in FIG. 6;

FIG. 9 is a view showing forms of the samples after the heat-resistanceevaluation;

FIGS. 10A to 10D are schematic process diagrams for describing a methodof forming a heat-resistant layer;

FIG. 11 is a schematic view showing an example of a structure of adeposition apparatus for a heat-resistant layer;

FIG. 12 is a schematic view showing another example of the structure ofthe deposition apparatus for a heat-resistant layer; and

FIG. 13 is a block diagram showing a structure of a battery packaccording to an embodiment of the present disclosure.

DETAILED DESCRIPTION

Hereinafter, embodiments of the present disclosure will be describedwith reference to the drawings.

First Embodiment Structure of Non-Aqueous Electrolyte Battery

FIG. 1 is a perspective view showing an example of a structure of anon-aqueous electrolyte battery including a battery separator accordingto an embodiment of the present disclosure. FIG. 2 is a cross-sectionalview, taken along the line I-I of FIG. 1, schematically showing anelectrode laminate structure of the non-aqueous electrolyte battery.

A non-aqueous electrolyte battery 20 according to this embodimentincludes a wound electrode body 10 to which a positive electrode lead 15and a negative electrode lead 16 are attached, and a film-like exteriormember 19 that houses the wound electrode body 10. The non-aqueouselectrolyte battery 20 is formed in a flat shape as a whole. Thepositive electrode lead 15 and the negative electrode lead 16 each havea strip shape and are each led out from the inside of the exteriormember 19 to the outside thereof, for example, in the same direction.The positive electrode lead 15 is formed of a metal material such asaluminum (Al) or stainless steel (SUS), and the negative electrode lead16 is formed of a metal material such as nickel (Ni).

[Exterior Member]

The exterior member 19 is, for example, a laminate film having astructure in which a thermal fusion layer, a metal layer, and anexterior resin layer are laminated in the stated order and bonded to oneanother by lamination or the like. In the exterior member 19, forexample, with the thermal fusion layer being inside, outer edge portionsof the layers are brought into intimate contact with one another byfusion or with an adhesive.

The thermal fusion layer is formed of, for example, a polyolefin resinsuch as polyethylene, polypropylene, modified polyethylene, modifiedpolypropylene, or a copolymer of them. This kind of resin material haslow moisture permeability and excellent hermeticity. The metal layer isformed of foil-like or plate-like aluminum, stainless steel, nickel,iron (Fe), or the like. The exterior resin layer may be formed of, forexample, the same resin used for the thermal fusion layer or may beformed of polyamide or the like. Accordingly, strength against breakage,penetration, and the like can be enhanced. The exterior member 19 mayinclude different layers other than the thermal fusion layer, the metallayer, and the exterior resin layer.

Between the exterior member 19 and the positive electrode lead 15 andnegative electrode lead 16, a contact film 17 for increasing adhesionbetween the positive electrode lead 15 and negative electrode lead 16and the inside of the exterior member 19 and preventing the entry ofoutside air is inserted. The contact film 17 is formed of a materialhaving adhesion to the positive electrode lead 15 and to the negativeelectrode lead 16. In the case where the positive electrode lead 15 andthe negative electrode lead 16 are formed of the metal materialsdescribed above, the contact film 17 is formed of, for example, apolyolefin resin such as polyethylene, polypropylene, modifiedpolyethylene, or modified polypropylene.

As shown in FIG. 2, the wound electrode body 10 is formed by laminatinga positive electrode 11 and a negative electrode 12 via a separator 13and an electrolyte layer 14 that is a non-liquid and non-aqueouselectrolyte and winding the laminate. A protective tape 18 is attachedto the outermost circumferential portion of the wound electrode body 10so that the wound state is maintained.

[Positive Electrode]

The positive electrode 11 includes a positive electrode currentcollector 11A and a positive electrode active material layer 11Bcontaining a positive electrode active material. The positive electrodeactive material layer 11B is formed on both surfaces of the positiveelectrode current collector 11A. As the positive electrode currentcollector 11A, for example, metal foils such as an aluminum foil, anickel foil, and a stainless steel foil can be used.

The positive electrode active material layer 11B contains, for example,the positive electrode active material, a conductive agent, and abinding agent. As the positive electrode active material, a metal oxide,a metal sulfide, or a specific polymer can be used in accordance withthe type of target battery. For example, in the case where a lithium-ionbattery is formed, a composite oxide formed of lithium (Li) and atransition metal is used. The composite oxide mainly contains Li_(X)MO₂(where M represents one or more kinds of transition metals, and X variesdepending on a charge or discharge state of the battery and normally hasa value of 0.05 or more and 1.10 or less). As the transition metals thatform the lithium composite oxide, cobalt (Co), nickel, manganese (Mn),and the like are used.

Specific examples of such a lithium composite oxide include LiCoO₂,LiNiO₂, LiMn₂O₄, and LiNi_(y)Co_(1-y)O₂ (0<y<1). Further, a solidsolution in which a part of a transition metal element is substitutedwith another element can also be used. Examples of the solid solutioninclude LiNi_(0.5)Co_(0.5)O₂ and LiNi_(0.8)Co_(0.2)O₂. Those lithiumcomposite oxides can generate a high voltage and are excellent in energydensity.

In addition, as the positive electrode active material, a metal sulfide,a metal oxide, and the like that contain no lithium, such as TiS₂, MoS₂,NbSe₂, and V₂O₅ may be used. Those positive electrode active materialsmay be used alone or in combination of various kinds thereof.

Examples of the conductive agent include carbon materials such asgraphite, carbon black, acetylene black, and ketjen black. Thosematerials may be used alone or in combination of various kinds thereof.It should be noted that the conductive agent may be a metal material ora conductive polymer as long as it is formed of a material havingconductivity.

Examples of the binding agent include a synthetic rubber such as astyrene-butadiene rubber, a fluoro rubber, an ethylene-propylene-dienerubber, and a polymeric material such as polyvinylidene fluoride. Thosematerials may be used alone or in combination of various kinds thereof.

The positive electrode 11 includes the positive electrode lead 15, whichis connected to an end portion of the positive electrode currentcollector 11A by spot welding or ultrasonic welding. A metal foil andmesh-like material is desirable for the positive electrode lead 15, butmaterials that are electrochemically and chemically stable and canestablish conduction may be used instead of metal without causingproblems.

[Negative Electrode]

The negative electrode 12 includes a negative electrode currentcollector 12A and a negative electrode active material layer 12Bcontaining a negative electrode active material. The negative electrodeactive material layer 12B is formed on both surfaces of the negativeelectrode current collector 12A. As the negative electrode currentcollector 12A, for example, metal foils such as a copper (Cu) foil, anickel foil, and a stainless steel foil can be used.

The negative electrode active material layer 12B contains, for example,the negative electrode active material and, as necessary, a conductiveagent and a binding agent. As the negative electrode active material, alithium metal, a lithium alloy, a carbon material capable of beingdoped/undoped with lithium, or a composite material of a metal materialand a carbon material is used. Specifically, examples of the carbonmaterial capable of being doped/undoped with lithium includegraphitizable carbon, non-graphitizable carbon having a lattice spacingin (002) surface of 0.37 nm or more, and graphite having a latticespacing in (002) surface of 0.34 nm or less. More specifically,pyrolytic carbons, cokes, a glass-like carbon fiber, a sintered body ofan organic polymer compound, an activated carbon, carbon blacks, and thelike are included. Of those, the cokes include a pitch coke, a needlecoke, a petroleum coke, and the like. The sintered body of an organicpolymer compound refers to one obtained by sintering a phenol resin, afuran resin, and the like at an appropriate temperature to becarbonized. Since a change in crystalline structure that accompaniesstorage and release of lithium is very small in the carbon material, ahigh energy density and excellent cycle characteristics are obtained,and the carbon material also functions as a conductive agent. It shouldbe noted that the shape of the carbon material may be any of fiber-like,spherical, granular, and scale-like shapes.

Further, as the material capable of being doped/undoped with lithium,polymers such as polyacetylene and polypyrrole and oxides such as SnO₂can be used.

In addition to the carbon material described above, examples of thenegative electrode material capable of storing and releasing lithiuminclude a material that can store and release lithium and also includesat least one kind of metal element and metalloid element as aconstituent element. With use of this type of material, a high energydensity can be obtained. Such a negative electrode material may be asimple substance, an alloy, or a compound of the metal element or themetalloid element, or may be a material containing, in at least a partthereof, one or two or more kinds of phases of them.

It should be noted that the “alloy” used herein includes, in addition toan alloy constituted of two kinds or more of metal elements, an alloycontaining one kind or more of metal elements and one kind or more ofmetalloid elements. Further, the “alloy” may include a nonmetal element.In the composition of the alloy, a solid solution, an eutectic (eutecticmixture), an intermetallic compound, or two kinds or more of them maycoexist.

Examples of the metal element or metalloid element described aboveinclude a lithium metal. Further, examples of metal element or metalloidelement capable of forming an alloy with lithium include magnesium (Mg),boron (B), aluminum, gallium (Ga), indium (In), silicon (Si), germanium(Ge), tin (Sn), lead (Pb), bismuth (Bi), cadmium (Cd), silver (Ag), zinc(Zn), hafnium (Hf), zirconium (Zr), yttrium (Y), palladium (Pd), andplatinum (Pt).

As the negative electrode material constituted of the metal element ormetalloid element capable of forming an alloy with lithium, a materialincluding as a constituent element at least one kind of metal elementand metalloid element of Group 14 in a long-period type periodic tableis used. For example, a material including as a constituent element atleast one kind of silicon and tin is used. Since this type of materialhas a large capability of storing and releasing lithium, a high energydensity can be obtained.

Examples of the negative electrode material including at least one kindof silicon and tin include a simple substance, an alloy, and a compoundof silicon, a simple substance, an alloy, and a compound of tin, and amaterial containing, in at least a part thereof, one or two or morekinds of phases of them.

Examples of the alloy of silicon include an alloy containing, as asecond constituent element other than silicon, at least one kindselected from the group consisting of tin, nickel, copper, iron, cobalt,manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony(Sb), and chromium (Cr). Examples of the compound of silicon include acompound containing oxygen (O) or carbon (C). The compound may containthe second constituent element described above in addition to silicon.

Example of the alloy or compound of silicon include SiB₂, SiB₆, Mg₂Si,Ni₂Si, TiSi₂, MoSi₂, CoSi₂, NiSi₂, CaSi₂, CrSi₂, Cu₅Si, FeSi₂, MnSi₂,NbSi₂, TaSi₂, VSi₂, WSi₂, ZnSi₂, SiC, Si₃N₄, Si₂N₂O, SiO_(v) (0<v≦2),and LiSiO.

Examples of the alloy of tin include an alloy containing, as a secondconstituent element other than tin, at least one kind selected from thegroup consisting of silicon, nickel, copper, iron, cobalt, manganese,zinc, bismuth, antimony, and chromium. Examples of the compound of tininclude a compound containing oxygen or carbon. The compound may containthe second constituent element described above in addition to tin.Examples of the alloy or compound of tin include SnO_(w) (0<w≦2),SnSiO₃, LiSnO, and Mg₂Sn.

[Separator]

FIGS. 3 and 4 are schematic cross-sectional views each showing anexample of a structure of the separator 13. The separator 13 shown inFIG. 3 includes a base material 130 and a heat-resistant layer 131. Theseparator 13 isolates the positive electrode 11 and the negativeelectrode 12 from each other in a battery and passes ions therethroughwhile preventing short circuit of current due to contact of both theelectrodes.

When being arranged in a battery, the separator 13 is disposed such thatthe heat-resistant layer 131 is opposed to at least the positiveelectrode, that is, at least the heat-resistant layer 131 is positionedbetween the positive electrode 11 and the base material 130. With thisstructure, the separator 13 can be protected from an oxidizingenvironment and a high-temperature environment around the positiveelectrode at a time of a high charge voltage.

In the non-aqueous electrolyte battery 20 of this embodiment, when thenon-aqueous electrolyte battery 20 is recharged, for example, lithiumions are released from the positive electrode 11 and stored in thenegative electrode 12 via a non-aqueous electrolyte solution impregnatedin the separator 13. On the other hand, when the non-aqueous electrolytebattery 20 is discharged, for example, lithium ions are released fromthe negative electrode 12 and stored in the positive electrode 11 viathe non-aqueous electrolyte solution impregnated in the separator 13.

[Base Material]

The base material 130 is formed of a heat-resistant microporoussubstance having excellent strength. For the base material 130, aninsulating resin material having a large ion permeation rate and apredetermined mechanical strength is typically used. Examples of such aresin material include polyolefin-based synthetic resins such aspolypropylene (PP) and polyethylene (PE), acrylic resins, styreneresins, polyester resins, and polyamide-based resins. In particular,polyethylene such as low-density polyethylene (LDPE), high-densitypolyethylene (HDPE), and linear polyethylene, a low molecular weight waxof them, or a polyolefin-based resin such as polypropylene isappropriate in terms of a melting temperature and easily available.Further, a laminate structure of two kinds or more of those porousmembranes or a porous membrane formed by fusing and kneading two kindsor more of resin materials may be adopted. A material containing apolyolefin-based porous membrane has excellent isolation performancebetween the positive electrode 11 and the negative electrode 12 and canfurther reduce internal short circuit and a lowering of an open-circuitvoltage.

A thickness of the base material 130 can be arbitrarily set as long as anecessary strength can be maintained with such a thickness. The basematerial 130 is set to have a thickness with which the positiveelectrode 11 and the negative electrode 12 are isolated from each other,short circuit and the like are prevented from occurring, ionpermeability for suitably performing a battery reaction via theseparator 13 is obtained, and a volumetric efficiency of an activematerial layer that contributes to a battery reaction in the battery canbe increased as much as possible. For example, the thickness of the basematerial 130 is set to 5 μm or more and 20 μm or less.

[Heat-Resistant Layer]

The heat-resistant layer 131 is formed on at least one surface of thebase material 130. The separator 13 shown in FIG. 3 is an example inwhich the heat-resistant layer 131 is formed on a first surface (uppersurface in FIG. 3) of the base material 130, and the separator 13 shownin FIG. 4 is an example in which the heat-resistant layer 131 is formedon each of the first surface of the base material 130 and a secondsurface (lower surface in FIG. 4) opposed to the first surface. Theheat-resistant layer 131 is for suppressing shrink of the base material130 due to heat while maintaining an excellent shutdown function of theseparator 13.

The heat-resistant layer 131 is formed of an inorganic material layerhaving heat resistance higher than that of a material constituting thebase material 130. Examples of such an inorganic material include analuminum oxide, a silicon oxide, and a titanium oxide. In thisembodiment, an aluminum oxide is used.

The heat-resistant layer 131 is formed not only on a main surface (onesurface or both surfaces) of the base material 130 but also inside thebase material 130. As described above, the base material 130 is formedof a microporous material and has a plurality of minute holesthereinside. Those holes are not only formed in a plane of the basematerial 130 (both surfaces thereof) but also continuously formed in athickness direction thereof such that one surface of the base material130 can communicate with the other surface. The heat-resistant layer 131is formed not only on the main surface of the base material 130 but alsoon the surface of each hole.

FIG. 5 is a cross-sectional view schematically showing an internalstructure of the separator 13. Inside the base material 130, a pluralityof passages 13T that cause the upper surface of the base material 130and the lower surface thereof to communicate with each other are formed.As described above, the base material 130 incorporates a plurality ofminute holes. The passages 13T are formed by the holes within the basematerial 130 being connected in the thickness direction. It should benoted that for simple description, the passages 13T are illustrated aslinear passages in FIG. 5.

An inner wall surface of each passage 13T is covered with theheat-resistant layer 131. The heat-resistant layer 131 that covers thepassages 13T is formed simultaneously with the heat-resistant layer 131that covers the main surface of the base material 130. In other words,the heat-resistant layer 131 is formed on the main surface of the basematerial 130 and the surface of each inner hole without clogging thepassages 13T (holes). Here, the hole of the base material 130 has aninner diameter of 50 nm or more and 100 nm or less, for example. Theheat-resistant layer 131 is formed on the surfaces of the holes havingsuch an inner diameter without clogging the holes.

The formation of the heat-resistant layer 131 on the surfaces of thepassages 13T can improve heat resistance of the separator 13 as comparedto the case where the heat-resistant layer 131 is formed only on themain surface of the base material 130. Further, the formation of theheat-resistant layer 131 on the surfaces of the passages 13T can enhanceaffinity of an electrolyte solution with respect to the passages 13T.

A thickness of the heat-resistant layer 131 is 2 nm or more and 10 nm orless, for example. In the case where the thickness is less than 2 nm,target heat resistance of the separator 13 is difficult to be obtained.On the other hand, when the thickness is larger than 10 nm, heatresistance is excessively raised and therefore it becomes difficult tostably ensure a predetermined shutdown function of the base material130. Further, the openings of the passages 13T are narrowed and airresistance is significantly increased.

FIG. 6 is a table of experiment results showing a relationship among athickness of the heat-resistant layer, air resistance (Gurley) of theseparator, and wettability. Here, the separator 13 having the structureshown in FIG. 3 was produced. For the base material 130, polyethylene(PE) having a thickness of 16 μm and air resistance of 300 [s/100 ml]was used. A temperature at which the holes are clogged due toself-contract of the base material (shutdown temperature) is generallyabout 100 to 150° C., though it depends on the quality of the basematerial. For the heat-resistant layer 131, an aluminum oxide was used.

The wettability was represented by a contact angle (degree) between thesurface of the separator 13 and dimethyl carbonate (DMC). The contactangle was defined as an angle θ formed, after a droplet L of DMC isformed on a surface S of the separator as shown in FIG. 7, between thesurface S and a tangent line 1 of a circle at a point a. Here, the pointa represents a contact point between the droplet L and the surface S.

As shown in FIG. 6, as compared to a sample 1 formed of only a basematerial having no heat-resistant layer, samples 2 to 4 each having aheat-resistant layer have a small contact angle with respect to DMC,which is measurement limit or less, and also have high wettability. Thisresults from physical properties as to whether the contact surface ofthe separator with DMC is the base material or the heat-resistant layer.In the separator of the non-aqueous electrolyte battery in which anelectrolyte solvent contains DMC, higher affinity with DMC is moredesirable, with which ion permeability is enhanced and batterycharacteristics can be improved.

On the other hand, it was found that the air resistance is reduced asthe thickness of the heat-resistant layer is increased, and the airresistance has a value of 2,000 or more at a thickness of 20 nm (sample4). The air resistance used herein means a time required for air of 100ml to pass. A smaller value of the air resistance of the separator ismore desirable. For example, the thickness of the heat-resistant layerto set the air resistance to 1,000 [s/100 ml] or less is 18 nm or less,and the thickness of the heat-resistant layer to set the air resistanceto 600 [s/100 ml] or less is 15 nm or less.

FIGS. 8 and 9 show experiment results showing heat resistance of thesamples 1 to 4. FIG. 8 shows contraction rates of length, in anarbitrary direction, of the samples formed in a rectangular shape,obtained after the samples are held at temperatures of 90° C., 105° C.,and 130° C. for one hour. The contraction rate used herein means arelative value when a dimension of a sample at room temperature isassumed to be 100(%). Meanwhile, FIG. 9 shows states of the samplesafter being held at 150° C. for one hour.

As shown in FIG. 8, contraction of the samples was found at thetemperature of 130° C. In particular, a contraction amount of the sample1 having no heat-resistant layer was large, and as shown in FIG. 9, thesample 1 hardly retained its original shape at the temperature of 150°C. On the other hand, in each of the samples 2 to 4 having aheat-resistant layer, a contraction amount was small as compared to thesample 1. As shown in FIG. 9, it was found that although the contractionforms are different, as the thickness of the heat-resistant layer islarger, contraction is less caused and higher heat resistance isobtained. It is obvious that use of a sample in which a heat-resistantlayer is formed on both surfaces of the base material as shown in FIG.4, instead of the structure of FIG. 3, can reduce thermal contractionmore than the experiment results described above.

Further, as shown in FIG. 9, while the samples 2 and 3 are translucentas a whole, the sample 4 is whitish as a whole. This means that theholes of the base material are clogged in the samples 2 and 3, and theholes of the base material are not yet clogged in the sample 4. In otherwords, this implies that the predetermined shutdown function of thesamples 2 and 3 works effectively, and conversely the shutdown functionof the sample 4 does not work effectively. This is considered because inthis example, the thickness of the heat-resistant layer of the sample 4is 20 nm, which is large, and a clogging operation of the holes by heatis inhibited.

Further, although not shown in the figures, the thickness of theheat-resistant layer 131 that covers one surface of the base material130, the other surface thereof, and the surfaces of the holes may bealmost uniform or different from one another. In the case where thethickness is different, for example, the thickness of the heat-resistantlayer 131 that covers the surface of the base material 130 may be largerthan that of the heat-resistant layer 131 that covers the surfaces ofthe holes.

Furthermore, the heat-resistant layer 131 that covers the surfaces ofthe holes may be formed in an almost uniform thickness or may have adistribution of thickness. For example, as a distance from the surface(both surfaces) of the base material 130 is increased in each hole, thethickness of the heat-resistant layer 131 may be gradually reduced.Alternatively, in the heat-resistant layer 131 that covers the surfacesof the holes, the thickness of the heat-resistant layer 131 formed atthe center in the thickness direction of the separator 13 (base material130) may be smaller than that of other portions. With this structure,spaces are generated in the holes of the separator 13, with the resultthat air resistance can be reduced (a degree of penetration of theelectrolyte solution is increased) while heat resistance is ensured.

[Non-Aqueous Electrolyte]

The electrolyte layer 14 contains a non-aqueous electrolyte solution anda polymer compound holding the non-aqueous electrolyte solution and isin a so-called gel state. The non-aqueous electrolyte solution containsan electrolyte salt and a solvent that dissolves the electrolyte salt.Examples of the electrolyte salt include lithium hexafluorophosphate(LiPF₆), lithium tetrafluoroborate (LiBF₄), lithium perchlorate(LiClO₄), lithium hexafluoroarsenate (LiAsF₆), lithium tetraphenylborate(LiB(C₆H₅)₄), lithium methanesulfonate (LiCH₃SO₃), lithiumtrifluoromethanesulfonate (LiCF₃SO₃), lithium tetrachloroaluminate(LiAlCl₄), dilithium hexafluorosilicate (Li₂SiF₆), lithium chloride(LiCl), and lithium bromide (LiBr). For the electrolyte salt, any onekind of them may be used, or two or more kinds of them may be used incombination.

Examples of the solvent include the following non-aqueous solvents:lactone-based solvents such as γ-butyrolactone, γ-valerolactone,δ-valerolactone, and ε-caprolactone; ester carbonate-based solvents suchas ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate(BC), vinylene carbonate (VC), dimethyl carbonate (DMC), ethyl methylcarbonate (EMC), and diethyl carbonate (DEC); ether-based solvents suchas 1,2-dimethoxyethane, 1-ethoxy-2-methoxyethane, 1,2-diethoxyethane,tetrahydrofuran, and 2-methyltetrahydrofuran; nitrile-based solventssuch as acetonitrile; sulfolane-based solvents; phosphoric acids;phosphate ester solvents; and pyrrolidones. For the solvent, any onekind of them may be used alone or two or more kinds of them may be usedin combination.

Further, it is desirable for the solvent to contain a compound in whicha part or all of hydrogen of a cyclic ester or a chained ester isfluorinated. As the fluorinated compound, it is desirable to usedifluoroethylene carbonate (4,5-difluoro-1,3-dioxolane-2-one). This isbecause, even when the negative electrode 12 containing a compound ofsilicon, tin, germanium, or the like is used as the negative electrodeactive material, charge-discharge cycle characteristics can be improved,and difluoroethylene carbonate is particularly excellent in the effectof improving cycle characteristics.

The polymer compound may be any compound that absorbs a solvent andturns the solvent into a gel. Examples of the polymer compound includefluorine-based polymer compounds such as a copolymer of polyvinylidenefluoride (PVdF) or vinylidene fluoride (VdF) and hexafluoropropylene(HFP), an ether-based polymer compound such as a polyethylene oxide(PEO) or a cross-linker containing a polyethylene oxide (PEO), and apolymer compound containing polyacrylonitrile (PAN), a polypropyleneoxide (PPO), or polymethylmethacrylate (PMMA) as a repeating unit. Forthe polymer compound, any one kind of them may be used alone, or two ormore kinds of them may be used in combination.

In particular, it is desirable to use a fluorine-based polymer compoundfrom the viewpoint of redox stability, and it is more desirable to use acopolymer containing vinylidene fluoride (VdF) and hexafluoropropylene(HFP) as its components. Further, the copolymer described above maycontain, as its components, an unsaturated dibasic acid monoester suchas monomethyl maleate (MME), a halogenated ethylene such aschlorotrifluoroethylene (PTCFE), a cyclic carbonate of an unsaturatedcompound such as vinylene carbonate (VC), an epoxy group-containingacrylic vinyl monomer, and the like. This is because highercharacteristics can be obtained.

[Method of Manufacturing Non-Aqueous Electrolyte Battery] [Method ofManufacturing Positive Electrode]

The positive electrode 11 is manufactured as follows. A positiveelectrode active material, a binding agent, and a conductive agent arefirst mixed to prepare a positive electrode mixture. The positiveelectrode mixture is dispersed in a solvent of N-methyl-2-pyrrolidone orthe like to prepare a mixed solution. Then, the positive electrodemixture slurry thus prepared is applied to the positive electrodecurrent collector 11A and dried, and then compression-molded with a rollpress machine or the like to form the positive electrode active materiallayer 11B, thus obtaining a positive electrode 11.

[Method of Manufacturing Negative Electrode]

The negative electrode 12 is manufactured as follows. A negativeelectrode active material and a binding agent are first mixed to preparea negative electrode mixture. The negative electrode mixture isdispersed in a solvent of N-methyl-2-pyrrolidone or the like to obtain anegative electrode mixture slurry. Then, the negative electrode mixtureslurry is applied to the negative electrode current collector 12A andthe solvent is dried, and then compression-molded with a roll pressmachine or the like to form the negative electrode active material layer12B, thus obtaining a negative electrode 12.

Further, in the case where a metal- or alloy-based negative electrode isused, a gas phase method, a liquid phase method, a thermal sprayingmethod, a calcination method, and the like can be used. Furthermore, inthe case where two kinds or more of those methods are used, it isdesirable for the negative electrode current collector 12A and thenegative electrode active material layer 12B to be alloyed in at least apart of an interface therebetween. Specifically, it is desirable that inthe interface, a constituent element of the negative electrode currentcollector 12A be dispersed in the negative electrode active materiallayer 12B, a constituent element of the negative electrode activematerial layer 12B be dispersed in the negative electrode currentcollector 12A, or those constituent elements be mutually dispersed.Accordingly, breaking of the negative electrode active material layer12B due to expansion and contraction accompanying the charge anddischarge can be suppressed, and electron conductivity between thenegative electrode active material layer 12B and the negative electrodecurrent collector 12A can be improved.

It should be noted that examples of the gas phase method includephysical vapor deposition and chemical vapor deposition, specificallyvacuum deposition, sputtering, ion plating, laser ablation, thermalchemical vapor deposition (CVD), and plasma CVD. As the liquid phasemethod, known techniques such as electroplating and electroless platingcan be used. For example, the calcination method is a method of applyinga granular negative electrode active material mixed with a binding agentor the like and dispersed in the solvent, and then performing heattreatment at a temperature higher than a melting point of the bindingagent or the like. A known method can also be used regarding thecalcination method, and for example, an atmospheric calcination method,a reactive calcination method, or a hot press calcination method may beused.

[Method of Manufacturing Separator]

The separator 13 is manufactured by forming the heat-resistant layer 131on one surface or both surfaces of the base material 130. Theheat-resistant layer 131 is deposited by an atomic layer depositionmethod (hereinafter, also referred to as ALD method). The ALD method isa thin-film forming method in which a plurality of kinds of source gases(precursor gases) are alternately introduced into a chamber so that areaction product is deposited as an atomic layer one by one on thesurface of a base material. Accordingly, the heat-resistant layer 131can be formed not only on the main surface of the base material 130 butalso on the surfaces of the holes (inner wall surfaces of the passages13T) formed in the base material 130 (FIG. 5).

[Method of Depositing Heat-Resistant Layer]

In the ALD method, a method of forming plasma in a chamber (plasma ALDmethod), a method of heating a base material (thermal ALD method), andthe like to promote a reaction of the source gases are known, and anymethod of them can be applied. In this embodiment, however, the thermalALD method is adopted.

In the case where the heat-resistant layer 131 is formed of an aluminumoxide film, a first precursor gas and a second precursor gas are used.Examples of the first precursor gas include TMA (trimethylaluminium;(CH₃)₃Al). Examples of the second precursor gas include water (H₂O).

It should be noted that in addition to the above materials, thefollowing materials can be used as the first and second precursor gases,for example: bis(tert-butylimino)bis(dimethylamino)tungsten (VI);((CH₃)₃CN)₂W(N(CH₃)₂)₂, tris(tert-butoxy)s Hanoi; ((CH₃)₃CO)₃SiOH,diethylzinc; (C₂H₅)₂Zn, tris(diethylamido)(tert-butylimido)tantalum (V);(CH₃)₃CNTa(N(C₂H₅)₂)₃, tris(tert-pentoxy)silanol; (CH₃CH₂C(CH₃)₂O)₃SiOH,trimethyl(methylcyclopentadienyl)platinum (IV); C₅H₄CH₃Pt(CH₃)₃,bis(ethylcyclopentadienyl)ruthenium (II); C₇H₉RuC₇H₉,(3-aminopropyl)triethoxysilane; H₂N(CH₂)₃Si(OC₂H₅)₃, silicontetrachloride; SiCl₄, titanium tetrachloride; TiCl₄, titanium (IV)isopropoxide; Ti[(OCH)(CH₃)₂]₄, tetrakis(dimethylamido)titanium (IV);[(CH₃)₂N]₄Ti, tetrakis(dimethylamido)zirconium (IV); [(CH₃)₂N]₄Zr,tris[N,N-bis(trimethylsilyl)amide]yttrium; and [[(CH₃)₃Si]₂]N)₃Y.

FIG. 10 are process diagrams for describing a method of depositing anALD layer. Here, a method of depositing an ALD layer 34 will bedescribed with an example of batch treatment. However, depositiontreatment in a roll-to-roll system can also be applied as describedlater.

As shown in FIGS. 10A to 10D, a porous base material film 35 issequentially exposed to a first precursor gas 36A, a purge gas 36P, asecond precursor gas 36B, and the purge gas 36P, to thereby form analuminum oxide monolayer 34C. The base material film 35 corresponds tothe base material 130 shown in FIG. 3 or 4. The base material film 35 isheated to a predetermined temperature at a time of deposition. Thepredetermined temperature is set to a lower temperature than a shutdowntemperature of the base material film 35.

The base material film 35 is brought in the chamber evacuated to apredetermined pressure. As shown in FIG. 10A, the first precursor gas36A introduced into the chamber is adsorbed on the surface of the basematerial film 35 so that a first precursor layer 34A formed of theprecursor gas 36A is formed on the surface of the base material film 35.

Then, as shown in FIG. 10B, the purge gas 36P is introduced into thechamber. Accordingly, the surface of the base material film 35 isexposed to the purge gas 36P, and the unattached precursor gas 36Aremaining on the surface of the base material film 35 is removed. As thepurge gas 36P, for example, argon (Ar) is used in the case where a thinfilm of an aluminum oxide is formed. In addition to argon, for example,nitrogen, hydrogen, oxygen, carbon dioxide, and the like can be used asa purge gas.

Subsequently, as shown in FIG. 10C, the second precursor gas 36B isintroduced into the chamber. The second precursor gas 36B is adsorbed onthe surface of the base material film 35 to thereby form a secondprecursor layer 34B formed of the precursor gas 36B on the firstprecursor layer 34A. As a result, an aluminum oxide monolayer 34C isformed by a chemical reaction between the first precursor layer 34A andthe second precursor layer 34B. After that, as shown in FIG. 10D, thepurge gas 36P is introduced into the chamber again, and the unattachedprecursor gas 36B remaining on the surface of the base material film 35is removed.

By repetition of the above treatment, an ALD layer 34 having apredetermined thickness is formed on the surface of the base materialfilm 35. The ALD layer 34 corresponds to the heat-resistant layer 131shown in FIG. 3 or 4. The heat-resistant layer 131 is formed not only onthe surface of the base material 130 but also on the surfaces of theholes (passages 13T) as shown in FIG. 5.

[Deposition Apparatus for Heat-Resistant Layer]

FIG. 11 is a cross-sectional view schematically showing an example of adeposition apparatus for forming the heat-resistant layer 131 by theroll-to-roll system. This deposition apparatus 100 is constituted as anapparatus for manufacturing a separator in which a heat-resistant layeris formed on one surface of a base material as shown in FIG. 3.

The deposition apparatus 100 includes a vacuum chamber 101 evacuated toa predetermined pressure, an inner chamber 102 filled with the purge gas36P, and a transfer mechanism for transferring the base material film 35that constitutes the base material 130 in the vacuum chamber 101. Thedeposition apparatus 100 additionally includes ALD heads 105A and 105Band a temperature control unit 106. The ALD heads 105A and 105Bdischarge the precursor gases 36A and 36B to the surface of the basematerial film 35 transferred inside the vacuum chamber 101. Thetemperature control unit 106 is installed in the outside of the vacuumchamber 101.

The transfer mechanism includes a pay-out roller that pays out the basematerial film 35, a take-up roller that takes up the base material film35, and a plurality of guide rolls 103 and 104 installed between thepay-out roller and the take-up roller. The plurality of guide rolls 103and the plurality of guide rolls 104 are arrayed in the outside of theopposed sidewall portions of the inner chamber 102. The base materialfilm 35 is transferred while being alternately guided by the guide rolls103 and the guide rolls 104. In this example, both the guide rolls 103and 104 are arranged such that the front surface (deposition surface) ofthe base material film 35 comes into contact with the guide rolls 103,and the rear surface (non-deposition surface) of the base material film35 comes into contact with the guide rolls 104. Further, the guide rolls103 and 104 are each configured such that its surface temperature can beadjusted in accordance with a command from the temperature control unit106. Accordingly, the base material film 35 is maintained at apredetermined deposition temperature.

Meanwhile, a plurality of slots are formed on both the sidewall portionsof the inner chamber 102. The base material film 35 can pass through theplurality of slots. Those slots are formed in areas through which thebase material film 35 linearly extending between the guide rolls 103 andthe guide rolls 104 passes. This allows the entrance and exit of thebase material film 35 to and from the inner chamber 102 each time thebase material film 35 passes through between the guide rolls 103 and theguide rolls 104.

The ALD heads 105A and 105B are arranged so as to face the respectiveguide rolls 103 and discharge the precursor gases 36A and 36B toward thesurface of the base material film 35 on the guide rolls 103. The ALDheads 105A discharge the first precursor gas 36A, and the other ALDheads 105B discharge the second precursor gas 36B. In this example, theALD heads 105A and 105B are alternately arranged along the transferdirection of the base material film 35 so as to face the guide rolls103.

It should be noted that the deposition apparatus 100 additionallyincludes an exhaust line for exhausting air from the vacuum chamber 101,a purge gas introduction line for supplying the purge gas 36P to theinner chamber 102, a precursor gas introduction line for supplying theprecursor gases to the ALD heads 105A and 105B, and the like, though notshown in the figure.

In the deposition apparatus 100 structured as described above, as shownin FIG. 11, the base material film 35 is sequentially transferred to thepositions of the ALD heads 105A and 105B by the transfer mechanismconstituted of the guide rolls 103 and 104 and the like. The basematerial film 35 is exposed to the first precursor gas 36A dischargedfrom the ALD head 105A (FIG. 10A) and then exposed to the purge gas 36Pin the inner chamber 102 (FIG. 10B). Subsequently, the base materialfilm 35 is exposed to the second precursor gas 36B discharged from theALD head 105B (FIG. 10C) and then exposed to the purge gas 36P in theinner chamber 102 (FIG. 10D). Such treatment is sequentially repeated sothat an ALD layer 34 is formed on the surface of the base material film35.

An amount, an exposure time, and the like of the precursor gases 36A and36B and the purge gas 36P, to which the base material film 35 isexposed, are adjusted based on a transfer speed of the base materialfilm 35, an amount of the gas discharged from the ALD heads 105A and105B, the size of the inner chamber 102, and the like.

In such a manner, the separator 13 shown in FIG. 3 is manufactured.Since the heat-resistant layer 131 is formed by the ALD method in thisembodiment, a dense film with high coverage performance can be obtained.Therefore, according to the separator 13 of this embodiment, theheat-resistant layer 131 can be formed not only on the main surface ofthe porous base material 130 but also on the surfaces of the minuteholes within the base material without clogging the holes. Accordingly,a separator 13 having excellent heat resistance can be obtained.

Further, the heat-resistant layer 131 is formed in a thickness of 2 nmor more and 10 nm or less, and accordingly heat resistance can beimproved while a predetermined shutdown function of the separator 13 isensured.

Meanwhile, FIG. 12 is a cross-sectional view schematically showing anexample of a deposition apparatus for forming the heat-resistant layer131 by the roll-to-roll system. This deposition apparatus 200 isconstituted as an apparatus for manufacturing a separator in which aheat-resistant layer is formed on both surfaces of a base material asshown in FIG. 4.

The deposition apparatus 200 shown in FIG. 12 has a structure in which aplurality of second ALD heads 107A and 107B are added to the depositionapparatus 100 shown in FIG. 11. Those ALD heads 107A and 107B arearranged so as to face the respective guide rolls 104 and discharge theprecursor gases 36A and 36B toward the rear surface of the base materialfilm 35 supported by the respective guide rolls 104. The ALD heads 107Adischarge the first precursor gas 36A, and the other ALD heads 107Bdischarge the second precursor gas 36B. Those ALD heads 107A and 107Bare alternately arranged along the transfer direction of the basematerial film 35 so as to face the respective guide rolls 104.

The base material film 35 faces the ALD heads 105A and 105B on its frontsurface side when being guided by the guide rolls 103 and faces the ALDheads 107A and 107B on its rear surface side when being guided by theguide rolls 104. Accordingly, an ALD layer (heat-resistant layer 131) isalternately formed on the front and rear surfaces of the base materialfilm 35.

[Method of Assembling Non-Aqueous Electrolyte Battery]

A precursor solution containing a non-aqueous solvent, an electrolytesalt, and as necessary, a solvent is first prepared. The precursorsolution is applied to the surface of each of the positive electrode 11and the negative electrode 12, and then the solvent is vaporized to forma gel-like electrolyte layer 14. Subsequently, the positive electrodelead 15 and the negative electrode lead 16 are attached to the positiveelectrode current collector 11A and the negative electrode currentcollector 12A, respectively. Here, the positive electrode lead 15 andthe negative electrode lead 16 may be attached to the positive electrodecurrent collector 11A and the negative electrode current collector 12A,respectively, before the electrolyte layer 14 is formed.

Subsequently, the positive electrode 11 and the negative electrode 12,on each of which the electrolyte layer 14 is formed, are laminated viathe separator 13 and wound in the longitudinal direction, and aprotective tape is bonded to the outermost circumferential portion ofthe laminate, to thereby form a wound electrode body 10. The woundelectrode body 10 can be continuously produced by the roll-to-rollsystem, for example. For the separator 13, the structure shown in FIG. 3may be used or the structure shown in FIG. 4 may be used.

Lastly, after the wound electrode body 10 is interposed between twofilm-like exterior members, for example, the exterior members are bondedto each other at their outer edge portions by thermal fusion bonding orthe like and sealed under reduced pressure, to thereby enclose the woundelectrode body 10. At this time, the contact film 17 is inserted betweenthe positive electrode lead 15 and negative electrode lead 16 and theexterior members. Thus, the non-aqueous electrolyte battery 20 isproduced.

Second Embodiment

The non-aqueous electrolyte battery 20 structured as described above ismounted to, for example, an electronic apparatus, an electric vehicle,and equipment such as an electric storage apparatus or can be used forsupplying power.

Examples of electronic apparatuses include a laptop personal computer, aPDA (personal digital assistant), a mobile phone, a cordless handset, avideo camera, a digital still camera, a digital book, an electronicdictionary, a music player, a radio, a headphone, a game machine, anavigation system, a memory card, a pacemaker, a hearing aid, anelectric tool, an electric shaver, a refrigerator, an air conditioner, atelevision set, a stereo, a water heater, a microwave, a dishwasher, awashing machine, a dryer, lighting equipment, a toy, medical equipment,a robot, a load conditioner, and a traffic light. In this case, examplesof power receiving circuits to which power is supplied from thenon-aqueous electrolyte battery 20 include an IC component, variouselectric/electronic components such as light emitting components, acircuit board on which those components are mounted, and an actuatorsuch as a motor.

Examples of electric vehicles include a railroad vehicle, a golf cart,an electric cart, and an electric automobile (including hybrid car). Thenon-aqueous electrolyte battery 20 is used as a driving power source oran auxiliary power source for those vehicles.

Examples of electric storage apparatuses include an electric-powerstorage power supply for buildings including houses or for electricpower generation facilities.

Hereinafter, a battery pack will be described as a typical example.

FIG. 13 is a block diagram showing an example of a circuit structure ofa battery pack including a secondary battery. A battery pack 300 mainlyincludes a cell 301, a switch unit 304, a control unit 310, and apackage body 320 that supports those components.

The battery pack 300 includes a positive electrode terminal 321 and anegative electrode terminal 322 and is recharged through the positiveelectrode terminal 321 and the negative electrode terminal 322 that areconnected to a positive electrode terminal and a negative electrodeterminal of a battery charger, respectively, at a time of charge.Further, at a time of using an electronic apparatus, the battery pack300 is discharged through the positive electrode terminal 321 and thenegative electrode terminal 322 that are connected to a positiveelectrode terminal and a negative electrode terminal of the electronicapparatus, to thereby supply power to a power receiving circuit of theelectronic apparatus.

The cell 301 is constituted of an assembled battery in which a pluralityof secondary batteries 301 a are connected to one another in seriesand/or in parallel. To the secondary batteries 301 a, the non-aqueouselectrolyte battery 20 described in the first embodiment is applied. Itshould be noted that FIG. 13 shows an example in which six secondarybatteries 301 a are connected to one another, two in parallel and threein series (2P3S configuration). In addition to this configuration, anyconnection method such as a configuration in which n batteries areconnected in parallel and m batteries are connected in series (n and mare integers) may be adopted.

The switch unit 304 includes a charge control switch 302 a, a diode 302b, and a discharge control switch 303 a, and a diode 303 b and iscontrolled by a switch control unit 314.

The diode 302 b has the polarity having an opposite direction withrespect to charge current flowing from the positive electrode terminal321 to the cell 301 and having a forward direction with respect todischarge current flowing from the negative electrode terminal 322 tothe cell 301. The diode 303 b has the polarity having a forwarddirection with respect to the charge current and having an oppositedirection with respect to the discharge current. It should be noted thatthe switch unit 304 is provided on the positive electrode terminal 321side, but it may be provided on the negative electrode terminal 322side.

In the case where a battery voltage reaches an overcharge detectionvoltage, the charge control switch 302 a is turned off and is controlledby the control unit 310 such that the charge current does not flow in acurrent path of the cell 301. After the charge control switch 302 a isturned off, only discharge can be performed via the diode 302 b.Further, in the case where a large amount of current flows at a time ofcharge, the charge control switch 302 a is turned off and is controlledby the control unit 310 such that the charge current flowing in thecurrent path of the cell 301 is shut off.

In the case where the battery voltage reaches an overdischarge detectionvoltage, the discharge control switch 303 a is turned off and iscontrolled by the control unit 310 such that the discharge current doesnot flow in the current path of the cell 301. After the dischargecontrol switch 303 a is turned off, only charge can be performed via thediode 303 b. Further, in the case where a large amount of current flowsat a time of discharge, the discharge control switch 303 a is turned offand is controlled by the control unit 310 such that the dischargecurrent flowing in the current path of the cell 301 is shut off.

A temperature detection element 308 is provided in the vicinity of thecell 301, and measures a temperature of the cell 301 and supplies themeasured temperature to a temperature measurement unit 318. Thetemperature detection element 308 is a thermistor, for example. Thetemperature measurement unit 318 supplies information on the temperaturemeasured using the temperature detection element 308 to the control unit310. The control unit 310 controls charge and discharge at a time ofabnormal heat generation based on the output of the temperaturemeasurement unit 318 or performs correction in calculation of theremaining capacity.

A voltage measurement unit 311 measures voltages of the cell 301 and ofthe secondary batteries 301 a that constitute the cell 301, A/D-convertsthe measured voltages, and supplies them to the control unit 310. Acurrent measurement unit 313 measures a current using a currentdetection resistor 307 and supplies the measured current to the controlunit 310.

The switch control unit 314 is controlled by the control unit 310, andcontrols the charge control switch 302 a and the discharge controlswitch 303 a of the switch unit 304 based on the voltage and currentthat are input from the voltage measurement unit 311 and the currentmeasurement unit 313. The switch control unit 314 transmits a controlsignal of the switch unit 304 when a voltage of any one of secondarybatteries 301 a reaches the overcharge detection voltage or less or theoverdischarge detection voltage or less, or a large amount of currentflows rapidly, to thereby prevents overcharge, overdischarge, andover-current charge and discharge.

Here, in the case of a lithium-ion secondary battery, an overchargedetection voltage is defined to be 4.20 V±0.05 V, for example, and anoverdischarge detection voltage is defined to be 2.4 V±0.1 V, forexample.

For the charge control switch 302 a and the discharge control switch 303a, a semiconductor switch such as a MOSFET (metal-oxide semiconductorfield-effect transistor) is used. In this case, parasitic diodes of theMOSFET function as diode units 302 b and 303 b. In the case wherep-channel FETs (field-effect transistors) are used as the charge controlswitch 302 a and the discharge control switch 303 a, the switch controlunit 314 supplies a control signal DO and a control signal CO to a gateof the charge control switch 302 a and that of the discharge controlswitch 303 a, respectively.

In the case where the charge control switch 302 a and the dischargecontrol switch 303 a are of p-channel type, the charge control switch302 a and the discharge control switch 303 a are turned on by a gatepotential lower than a source potential by a predetermined value ormore. In other words, in normal charge and discharge operations, thecontrol signals CO and DO are determined to be a low level and thecharge control switch 302 a and the discharge control switch 303 a areturned off.

A memory 317 is constituted of a RAM (random access memory), a ROM (readonly memory), an EPROM (erasable programmable read only memory) servingas a nonvolatile memory, or the like. In the memory 317, numericalvalues computed by the control unit 310, an internal resistance value ofa battery in an initial state of each secondary battery 301 a, which hasbeen measured in a stage of a manufacturing process, and the like arestored in advance, and can be rewritten as appropriate. Further, when afull charge capacity of the secondary battery 301 a is stored, forexample, a remaining capacity can be calculated together with thecontrol unit 310.

Although the embodiments of the present disclosure have been describedabove, the present disclosure is not limited thereto. The presentdisclosure can be variously modified based on the technical ideas of thepresent disclosure.

In the embodiments described above, for example, the lithium-ionsecondary battery has been described as an example, but the presentdisclosure is not limited thereto. The present disclosure is alsoapplicable to a nickel hydrogen battery, a nickel cadmium battery, alithium-manganese dioxide battery, a lithium-iron sulfide battery, andseparators for those batteries.

Further, although the non-aqueous electrolyte secondary battery having awound structure has been described in the embodiments described above,in addition thereto, the present disclosure is similarly applicable to abattery having a structure in which a positive electrode and a negativeelectrode are folded back or laminated. In addition, the presentdisclosure is also applicable to batteries of a so-called coin type,button type, square type, and the like. Furthermore, the presentdisclosure is also applicable to a primary battery without being limitedto a secondary battery.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present subjectmatter and without diminishing its intended advantages. It is thereforeintended that such changes and modifications be covered by the appendedclaims.

The invention is claimed as follows:
 1. A battery separator, comprising:a porous base material including a first surface, a second surfaceopposed to the first surface, and a hole that is formed in the porousbase material and causes the first surface and the second surface tocommunicate with each other; and a heat-resistant layer configured tocover at least the first surface and a surface of the hole, theheat-resistant layer being formed of an inorganic material and depositedby an atomic layer deposition method.
 2. The battery separator accordingto claim 1, wherein the heat-resistant layer has a thickness of 2 nm ormore and 10 nm or less.
 3. The battery separator according to claim 1,wherein the heat-resistant layer covers the first surface, the secondsurface, and the surface of the hole.
 4. The battery separator accordingto claim 1, wherein the inorganic material is any one of an aluminumoxide, a silicon oxide, and a titanium oxide.
 5. The battery separatoraccording to claim 1, wherein the base material is a polyolefin-basedresin.
 6. The battery separator according to claim 1, wherein the basematerial has a thickness of 5 nm or more and 20 nm or less.
 7. Thebattery separator according to claim 1, wherein the hole has an innerdiameter of 50 nm or more and 100 nm or less.
 8. A method ofmanufacturing a battery separator, comprising: preparing a porous basematerial including a first surface, a second surface opposed to thefirst surface, and a hole that is formed in the porous base material andcauses the first surface and the second surface to communicate with eachother; and forming a heat-resistant layer by an atomic layer depositionmethod, the heat-resistant layer being configured to cover at least thefirst surface and a surface of the hole and being formed of an inorganicmaterial.
 9. The method of manufacturing a battery separator accordingto claim 8, wherein the heat-resistant layer is alternately formed onthe first surface and the second surface.
 10. A battery, comprising: apositive electrode; a negative electrode; an electrolyte layer arrangedbetween the positive electrode and the negative electrode; and aseparator including a porous base material including a first surfaceopposed to the positive electrode, a second surface opposed to thenegative electrode, and a hole that is formed in the porous basematerial and causes the first surface and the second surface tocommunicate with each other, and a heat-resistant layer to cover atleast the first surface and a surface of the hole, the heat-resistantlayer being formed of an inorganic material and deposited by an atomiclayer deposition method.
 11. A battery pack, comprising: a batteryincluding a positive electrode, a negative electrode, an electrolytelayer arranged between the positive electrode and the negativeelectrode, and a separator including a porous base material including afirst surface opposed to the positive electrode, a second surfaceopposed to the negative electrode, and a hole that is formed in theporous base material and causes the first surface and the second surfaceto communicate with each other, and a heat-resistant layer to cover atleast the first surface and a surface of the hole, the heat-resistantlayer being formed of an inorganic material and deposited by an atomiclayer deposition method; a control unit configured to control charge anddischarge of the battery; and a package body configured to support thebattery and the control unit.
 12. An electronic apparatus, comprising: abattery including a positive electrode, a negative electrode, anelectrolyte layer arranged between the positive electrode and thenegative electrode, and a separator including a porous base materialincluding a first surface opposed to the positive electrode, a secondsurface opposed to the negative electrode, and a hole that is formed inthe porous base material and causes the first surface and the secondsurface to communicate with each other, and a heat-resistant layer tocover at least the first surface and a surface of the hole, theheat-resistant layer being formed of an inorganic material and depositedby an atomic layer deposition method; and a power receiving circuitconfigured to receive power supply from the battery.